Dynamics of component carbon fluxes in a semi-arid Acacia woodland, central Australia

Authors

  • James Cleverly,

    Corresponding author
    • School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Nicolas Boulain,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Randol Villalobos-Vega,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Nicole Grant,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Ralph Faux,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Cameron Wood,

    1. National Centre for Groundwater Research and Training, School of Environment, Flinders University, Adelaide, South Australia, Australia
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  • Peter G. Cook,

    1. National Centre for Groundwater Research and Training, School of Environment, Flinders University, Adelaide, South Australia, Australia
    2. Water for a Healthy Country National Research Flagship, Division of Land and Water, Commonwealth Scientific and Industrial Research Organization, Adelaide, South Australia, Australia
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  • Qiang Yu,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Andrea Leigh,

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
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  • Derek Eamus

    1. School of the Environment, University of Technology Sydney, Broadway, New South Wales, Australia
    2. National Centre for Groundwater Research and Training, University of Technology Sydney, Broadway, New South Wales, Australia
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Corresponding author: J. Cleverly, School of the Environment, University of Technology Sydney, PO Box 123, Broadway, NSW 2007, Australia. (James.Cleverly@UTS.edu.au)

Abstract

[1] Vast areas in the interior of Australia are exposed to regular but infrequent periods of heavy rainfall, interspersed with long periods at high temperatures, but little is known of the carbon budget of these remote areas or how they respond to extreme precipitation. In this study, we applied three methods to partition net ecosystem photosynthesis into gross primary production (GPP) and ecosystem respiration (Re) during two years of contrasting rainfall. The first year was wet (>250 mm above average rainfall), while little precipitation fell during the second year (>100 mm below average). During the first year of study, rates of GPP were large (793 g C m−2 yr−1) in this semi-arid Mulga (Acacia aneura) and grass savanna due to complementary photosynthetic responses by the canopy and C4 understorey to cycles of heavy rainfall. Patterns in GPP during the summer and autumn matched those in leaf area index (LAI), photosynthetic activity, and autotrophic respiration. During the dry year, small but positive photosynthetic uptake by Mulga contributed to the neutral carbon budget (GPP / Re = 1.06 ± 0.03). Small rates of photosynthesis by evergreen Mulga when dry were supported by storage of soil moisture above a relatively shallow hardpan. Little soil organic matter (1.1%) was available to support heterotrophic respiration (Rh) without input of fresh substrate. The two largest sources of Re in this study were autotrophic respiration by the seasonal understorey and Rh through decomposition of fresh organic matter supplied by the senescent understorey.

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